A process for the preparation of aluminosilicates in which surface-active compounds or tensides, which are resistant to the hardness of water are contained in a bound form therein has been disclosed in German Published Application (DOS) No. 2,439,572. A corresponding U.S. application was filed as Ser. No. 811,964, on June 6, 1977, now U.S. Pat. No. 4,126,574. The products are obtained by precipitation resulting from the reaction of water-soluble silicates with water-soluble aluminates in the presence of water and surfactants. This precipitation is preferably carried out by mixing an aqueous aluminate solution with an aqueous silicate solution, the tensides preferably being present in the silicate solution.
The products of the above process are finely divided, X-ray amorphous aluminosilicates which contain tensides in a bound form as well as bound water and which, based on the tenside-free and anhydrous form, have the composition: EQU 0.7-1.5 Me.sub.2 O.multidot.Al.sub.2 O.sub.3 .multidot.0.8-6 SiO.sub.2,
wherein Me.sub.2 O is preferably an alkali metal oxide, in particular Na.sub.2 O. The compounds have a marked calcium binding capacity, amounting to 50 to 200 mg CaO/gm of anhydrous active substance, and an exceptionally high suspension stability in water. The water content of the dried products is generally in the region of from 3 to 8 mols per mol of Al.sub.2 O.sub.3 (8% to 45% by weight).
In the process according to German DOS No. 2,439,572, the preferred alkali metal aluminosilicates are obtained from alkali metal aluminates and alkali metal silicates, generally in the commercial form, which have a certain, fixed ratio of Me.sub.2 O/Al.sub.2 O.sub.3 and Me.sub.2 O/SiO.sub.2. If, using the given aluminate and silicate solutions, the quantities of aluminate and of silicate are calculated according to the desired Al.sub.2 O.sub.3 /SiO.sub.2 ratio in the end product so that no excess aluminate or silicate is present in the mother liquor of the product, then the quantity of alkali metal in the reaction mixture can no longer be freely chosen. This means, however, that the reaction mixture for the precipitation in most cases contains more alkali metal than corresponds to the composition of the desired product. Although a high proportion of the surplus alkali used is removed with the mother liquor when the precipitation product is isolated, the remainder is left in the precipitation product and increases the alkalinity in the interior of the individual particles. It is this enclosed alkali which will hereinafter be referred to as "excess alkali."
Although excess alkali may in some cases be advantageous, for example, as a reserve of alkali when aluminosilicates are used in washing liquors, the use of aluminosilicates with excess alkali in agents which are required to have a low pH gives rise to difficulties in adjustment of the pH since it may take days or even weeks to reach a constant pH due to the delayed release of excess alkali enclosed in the particles.
Another serious disadvantage of the excess alkali is its effect on the tensides contained in the products, especially at elevated temperatures or on prolonged storage. Cationic tensides, which are sensitive to alkali, are particularly seriously affected so that the products gradually turn yellow and develop an unpleasant smell.
To overcome these and other disadvantages, the excess alkali had to be removed by washing or neutralization which requires large quantities of water and prolonged washing. In addition, such a procedure would entail the risk of removing the surfactants which are also enclosed in the particles, in which case the products would lose their special properties.